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UDP Helper Configuration 303
To delete this feature, enter:
<SW5500>system-view
[SW5500]acl number 2500
[SW5500-acl-basic-2500]undo rule 0
UDP Helper
Configuration
This section contains UDP Helper configuration information.
Overview of UDP Helper The major function of the UDP Helper is to relay-forward UDP broadcast packets, that
is, it can convert UDP broadcast packets into unicast packets and send them to the
designated server, as a relay.
When UDP Helper starts, the Switch can judge whether to forward the UDP broadcast
packets received at the port based on UDP port ID. If yes, the Switch then modifies
the IP address in the IP packet header and sends the packet to the designated
destination server. Otherwise, it sends the packet to the upper layer module for
further processing. For the BOOTP/DHCP broadcast packet, if the client specifies in
the request message that the response message needs to be received as broadcast
packet, then the Switch broadcasts the response message to the client. Otherwise, it
unicasts the response message.
UDP Helper
Configuration
UDP Helper configuration includes:
■ Enabling/Disabling UDP Helper Function
■ Configuring UDP Port with Replay Function
■ Configuring the Relay Destination Server for Broadcast Packet
Enabling/Disabling UDP Helper Function
When the UDP Helper function is enabled, you can configure the UDP ports where
UDP function is required and the relay function is enabled at UDP ports 69, 53, 37,
137, 138, and 49. When the function is disabled, the relay function configured at all
UDP ports, including the default six ports, is disabled.
Perform the following configuration in System View.
By default, the UDP Helper function is disabled.
Configuring UDP Port with Replay Function
When the UDP relay function is enabled, by default the system forwards the
broadcast packets on the UDP ports listed in Table 300. You can configure up to 256
UDP ports with the relay function.
Table 299 Enabling/Disabling UDP Helper function
Operation Command
Enable UDP Helper function udp-helper enable
Disable UDP Helper function undo udp-helper enable
Table 300 Default UDP Ports List
Protocol UDP port ID
Trivial File Transfer Protocol (TFTP) 69
Domain Name System (DNS) 53
Time service 37